A quantitative scheme is put forward in our work of forecasting the storm rainfall of typhoons for specific sites. Using the initial parameters, weather situations and physical quantities as well as numerical weather prediction products, the scheme constructs multivariate, objective and similarity criteria for environmental factors for the time between the current and forthcoming moment within the domain of forecast. Through defining a non-linear similarity index, this work presents a comprehensive assessment of the similarity between historical samples of typhoons and those being forecast in terms of continuous dynamic states under the multivariate criteria in order to identify similar samples. The historical rainfall records of the similar samples are used to run weighted summarization of the similarity index to determine site-specific and quantitative forecasts of future typhoon rainfall. Samples resembling the typhoon being forecast are selected by defining a non-linear similarity index composed of multiple criteria. Trial tests have demonstrated that this scheme has positive prediction skill.
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The relationship between the self-organization of double vortices (SODVs) and the formation of typhoons was discussed based on six numerical experiments with the Fifth-Generation National Center for Atmospheric Research/Penn State Mesoscale Model (MM5) and further discussion was made with a real typhoon case. The results showed that there is a critical distance dc for SODVs in baroclinic atmosphere. When the distance between separated vortices is smaller than or equal to dc, the double vortices self-organize into a typhoon-like vortex with two spiral bands. But the double vortices cannot have such organization if the distance between them is larger than dc. The value of dc is about 380 km in the context of ideal conditions in this paper, larger than that achieved in a barotropic model. A typical typhoon case in 2005 (Haitang) was selected to verify the above-mentioned conclusions. It was found that the SODV is one of the important and typical ways for the formation of typhoons.
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With data of precipitation from 1971 to 2008 in local weather stations, and disaster data, geographical landscape and socio-economic background from 1983 to 2008 of 62 counties in Zhejiang Province, we performed dominance analysis methods, two weft graphics cluster, data envelop analysis, cluster analysis and hierarchy analysis, etc, to divide Zhejiang Province into five geographical districts based on these data, and then analyzed the relationship between the rainstorm disaster and hazard factors, geographical landscape, socio-economic background. The high-resolution assessment model of rainstorm-causing disaster intensity was established on the basis of the analyses, and the early warning index was calculated through the model. The early warning index of rainstorm-causing disaster of each geographical district is divided into 5 grades, with Grade 1 the highest. It is defined that Grade 1 are those that cause casualties and serious property losses which may lead to ultra-serious disaster; Grade 2 are those that cause very serious disasters; Grade 3 are those that likely cause severe damage; Grade 4 are for minor damage, and Grade 5 corresponds to no disasters. Tests show that the early warning index of rainstorm-causing disaster can reflect the actual disaster situations, and it can be applied to rainstorm disaster grade forecasting and disaster assessment.
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